This invention relates generally to building ventilation systems. More particularly, the present invention relates to building ventilation systems having apparatus for recovering the heat in the air exhausted from the ventilated area.
Ventilating systems are commonly used to maintain indoor environmental standards in industrial buildings, commercial office buildings, schools and farming facilities. Such buildings include foundries, factories, metal finishing areas, work shops, service areas, warehouses, meeting halls, recreational buildings, animal nursery and feeder houses, swimming pools and other facilities of many diverse types. Ventilation systems for such facilities are necessary to remove excess heat, discharge pollutants and unwanted moisture and to maintain a healthful, comfortable environment. Unfortunately, safety, health and economic considerations are at odds with one another in that air, which has been heated or cooled at substantial expense, is virtually thrown away by the conventional ventilation process.
In the case of a heated facility, the exhaust air of the ventilation process contains not only the sensible energy expended in increasing the supply air temperature but the latent energy represented by the vaporized water required to adequately humidify. With great pressure on power-producing utilities and the ever-increasing cost of fuels for heating and cooling, there is a great need to recover thermal energy from the exhaust air of all high performance ventilation systems.
Conventional ventilation thermal energy recovery systems have used rotating wheel heat exchangers as well as non-rotating cross-flow heat exchangers. Heat exchangers of these types have been constructed from metals such as stainless steel and aluminum and from certain ceramics such as aluminum oxide and silicon carbide. Such materials, while structurally sound, are expensive and have little or no capability of storing and releasing moisture not to mention the high maintenance required and lack of ability to provide free cooling when energy is not required to be recovered.
Briefly stated, the invention in a preferred form is an air-to-air heat recovery system for use with a building ventilation system. The heat recovery system is adapted for installation anywhere on or within the building and comprises first and second heat exchange banks and at least one damper module. Each of the heat exchange banks includes at least one heat exchange module having a heat exchange mass. Each heat exchange bank forms a flow path having oppositely disposed first and second ends. Each damper module includes a damper disposed within a substantially rectangular housing having first, second, third, and fourth ports. The first port is connected to the air exhaust line of the ventilation system, the second port is connected to the air supply line of the ventilation system, the third port is connected to the first end of the first heat exchange bank, and the fourth port is connected to the first end of the second heat exchange bank. The damper is periodically reciprocated between first and second positions, directing air flow between the first port and the third port and between the second port and the fourth port in the first position, and directing air flow between the first port and the fourth port and between the second port and the third port in the second position. The second end of each heat exchange bank is connected to the outside such that substantially no stale air is drawn into the air supply line when the damper is reciprocated.
The heat exchange mass of each heat exchange module includes a plurality of corrugated aluminum plates defining parallel 4 mm flow channels. A housing composed of steel surrounds the heat exchange mass and is separated from the heat exchange mass by an electrically non-conductive lining.
If the heat exchanger is to be installed on the outside of the building, the second end of each heat exchange bank is receives fresh air from the outside without any intervening ducting.
If the heat exchanger is to be installed on the inside of the building with one of the heat exchange banks receiving fresh air from the outside without any intervening ducting, the heat exchanger further comprises a duct and a second damper module. The duct has first and second ends located at an outside surface of the building and is connected to the second end of the second heat exchange bank at a position intermediate the first and second ends. The second damper module is positioned in the duct proximate to the second end of the second heat exchange bank. The first and second damper modules are simultaneously reciprocated between the first and second positions, with the damper of the second damper module directing air flow between the second port and the third port in the first position and between the first port and the third port in the second position.
If the heat exchanger is to be installed on the inside of the building with neither of the heat exchange banks receiving fresh air from the outside without any intervening ducting, the heat exchanger further comprises first and second ducts and second and third damper modules. Each of the ducts has first and second ends located at an outside surface of the building. The first duct is connected to the second end of the first heat exchange bank at a position intermediate the first and second ends and the second duct is connected to the second end of the second heat exchange bank at a position intermediate the first and second ends. The second damper module is positioned in the second duct proximate to the second end of the second heat exchange bank and the third damper module is positioned in the first duct proximate to the second end of the first heat exchange bank. The dampers of the first, second and third damper modules are simultaneously reciprocated between the first and second positions, with the damper of the second damper module directing air flow between the first port and the third port in the first position and between the second port and the third port in the second position and the damper of the third damper module directing air flow between the second port and the third port in the first position and between the first port and the third port in the second position.
It is an object of the invention to provide an air-to-air heat recovery system which may be installed anywhere on or within a building.
It is also an object of the invention to provide an air-to-air heat recovery system which has substantially no cross-contamination of the air.
Other objects and advantages of the invention will become apparent from the drawings and specification.